1. Field of the Invention
The present invention relates to control of image recording using a recording head and particularly to recording control according to inclination (misalignment) of a recording head or nozzle rows (nozzle array) of a recording head.
2. Description of the Related Art
A serial scanning type recording apparatus performs recording by using a recording head (print head) having element rows (also referred to hereinafter as “nozzle rows” and/or “nozzle array”), each containing recording elements (e.g., nozzles from which ink is discharged) arranged in a direction orthogonal to a main scanning direction. The recording apparatus performs printing while scanning a recording medium with the recording head, and transports the recording medium in a sub-scanning direction (which is orthogonal to the main scanning direction). The recording apparatus thus repeats the scanning and transporting process, thereby forming an image on the recording medium.
A typical print head is secured to a carriage holder (hereinafter called “carriage”). Since the print head is positioned such that nozzle rows (nozzle array) thereof are orthogonal to the main scanning direction, dots can be accurately arranged on a recording medium when ink is ejected during the scanning of the recording medium. However, due to manufacturing tolerances and assembly errors, nozzle rows (nozzle array) of the print head are, in fact, often not orthogonal to the main scanning direction. Moreover, the amount of inclination of nozzle rows (nozzle array) caused by assembly errors of the print head may not be consistent and may change every time the user attaches the print head to the recording apparatus.
The inclination of nozzle rows (nozzle array) causes misalignment of lines and colors on a printed image and leads to degraded image quality. Since recent tendencies toward longer and greater number of nozzle rows (nozzle array) and higher resolution cause more noticeable misalignment of lines and colors, a need exists to develop mechanisms for correcting the inclination of nozzle rows (nozzle array).
There is a proposed recording apparatus in which a plurality of heating dots are divided into a predetermined number of heating dot groups according to the amount of inclination of a print head, and print timing is shifted at each heating dot group so as to correct the inclination of the print head. If the amount of head inclination “D” is in the range of [N dots<D≦(N+1) dots] on a print dot basis, a plurality of heating dots are divided into (N+1) heating dot groups. Then, from the first heating dot group at which to start printing, print timing is shifted by one dot at each heating dot group to perform printing.
This print timing is divided into a plurality of segments (blocks) within a period of a pulse signal corresponding to one column (one pixel).
In this recording apparatus, print data that is shifted in a print direction on a dot-by-dot basis is expanded (stored) in an image buffer. Then, after the addition of off-dot data to be used for correction, print timing is shifted to correct the inclination of the print head.
Such a recording apparatus is discussed, for example, in Japanese Patent Laid-Open No. 11-42803 and Japanese Patent Laid-Open No. 7-137240.
However, in the known techniques described above, data that is shifted on a dot-by-dot basis has to be stored in the image buffer. Therefore, if the amount of data increases due to the increased length of a print head or the increased number of nozzle rows (nozzle array) for multiple ink colors, a problem arises in that a heavier load is placed on control for data processing.
Moreover, in timing control discussed in Japanese Patent Laid-Open No. 7-137240, timing adjustment through split driving can be performed only within the range (timing) of one pixel and cannot be performed over the range of one pixel.